Device for immobilizing a primary instrument and method therefor

ABSTRACT

Devices and methods provide accurate targeting, placement, and/or stabilization of an electrode or other instrument(s) into the brain or other body organ, such as to treat severe tremor or other neurological disorders. Targeting is performed using any form of image-guidance, including real-time MRI, CT, or frameless surgical navigation systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/899,677 filed on Oct. 7, 2010 now U.S. Pat. No. 8,911,452 issued onDec. 16, 2014, which is a continuation of U.S. patent application Ser.No. 11/768,077 filed on Jun. 25, 2007, now U.S. Pat. No. 7,833,231issued on Nov. 16, 2010, which is a divisional of U.S. patentapplication Ser. No. 10/175,668 filed Jun. 20, 2002, now U.S. Pat. No.7,235,084 issued on Jun. 26, 2007, which is a continuation applicationof U.S. patent application Ser. No. 09/828,451 filed on Apr. 6, 2001,now U.S. Pat. No. 7,204,840 issued on Apr. 17, 2007, which claimsbenefit to U.S. Provisional Patent Application No. 60/195,663 filed Apr.7, 2000. The entire disclosures of each of the above applications areincorporated herein by reference.

FIELD

This document relates generally to, among other things, surgicalplacement of a medical instrument deeply into an organ, such as a brain,and specifically, but not by way of limitation, to accurate targeting,placement, and/or acute or chronic stabilization of such an instrument.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

In placing a medical device or instrument deeply into an organ, such asa brain, it is often advantageous to precisely target, place, and thensecure the device for a period of time that may be several days or evenindefinitely. Examples of such devices include catheters, needles, anddrug and biological agent delivery instruments, as well as electricalmapping, stimulating and/or ablation leads.

Targeting such a device is not always an exact science. The target isnot always visible from preoperative images. Even when usingimage-guided minimally invasive techniques, with such imaging modalitiesmagnetic resonance imaging (MRI), computed tomography (CT), framelesssurgical navigation systems, and the like, there is often a need forsome tweaking or small adjustment in trajectory to accurately hit thetarget. A single trajectory approach would mean that the need to movethe target slightly laterally would require removing the device and thenreintroducing it, sometimes as close as 2 mm away from the originalentry site.

One approach to positioning an instrument, such as a deep brainstimulation electrode, uses a conventional stereotactic frame systemthat is secured to the patient. In this approach, preoperative images ofthe patient are used to determine the proper trajectory to the target,as measured and aligned relative to the frame. Using accessories mountedto the frame, the electrode is aligned and advanced through a burr holein the skull to the predetermined target. A base is then inserted intoand/or around the burr hole. Various “tool holes” and slots in the baseare deformed as the base is slid over the electrode. The tool holes inthe base are squeezed together as the base is inserted into the burrhole. When the base is released, it springs back outward against theinside diameter of the burr hole. The stereotactic accessories must thenbe carefully removed while holding the device in place. This step can beclumsy and inexact. If the electrode moves, it must be repositioned.Before securing the carefully-positioned device to the patient, theequipment used to introduce the device and maintain trajectory must beremoved. This action can often dislodge the device requiring the entireplacement procedure to be repeated. Even after the stereotacticaccessories have been removed, the electrode or other device must besecured. This procedure may also cause electrode movement. In oneexample, a silicone rubber cap is fit into place to capture and protectthe electrode. Placing the rubber cap may cause further electrodemovement.

One disadvantage of this approach is that the instrument positioning isattempted using only a presumed target location, based on thepreoperative images, and not an actual determination of the neededtrajectory to the target. Another disadvantage is that the stereotacticframe system is both expensive and unwieldy. Yet another disadvantage isthat the electrode may move at any one of several times during theprocedure and therefore require repositioning. For these and otherreasons, the present inventors have recognized that there is a need forimproved targeting, placement, and secure stabilization of a deep brainelectrode or other medical instrument.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

This document discusses, among other things a device and method forinstrument targeting, placement, and/or stabilization. This system maybe used with any instrument, but it is particularly useful with a deepbrain neurological stimulation electrode to treat severe tremor or otherdisorders. The system allows any of a number of imaging modalities,including MRI, CT, and frameless surgical navigation. The MRIenvironment typically provides both real-time brain images and real-timeMRI imaging of trajectory-alignment fiducial markings, althoughpreoperative MRI images of the brain could also be used. The framelesssurgical navigation typically uses retrospective brain images (e.g.,previously-acquired preoperative MRI images of the brain) and real-timeimaging recognition of trajectory-alignment fiducial markings (e.g.,using light-emitting diodes, reflective globes, etc.). Bothenvironments, therefore, provide image-guided alignment of theinstrument's trajectory to the target location. Such techniques provideaccurate placement of the electrode or other medical instrument. It alsoprovides acute and/or chronic stabilization of the instrument. Thesystem includes, among other things, an alignment/targeting system, aninstrument introducer system, and a stabilizer system. Other aspects ofthe present system and methods will become apparent upon reading thefollowing detailed description of the invention and viewing the drawingsthat form a part thereof.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a cross-sectional view example of an electrode that has beenimplanted and secured using the devices and methods discussed herein.

FIG. 2 is a perspective view example of a base and a cap.

FIG. 3 is an exploded perspective view example of an assembly of a base,a stabilizer, and a cap.

FIG. 4 is a perspective view example of a stabilizer.

FIG. 5 is an exploded perspective view example of a base, a stabilizer,and a cap.

FIGS. 6A and 6B provide two perspective view examples of a base and aburr-hole centering device.

FIG. 7 is a perspective view example of a tool for placing thestabilizer, securing the introduced instrument, and removing the cap.

FIG. 8 is a perspective view example of an instrument-securing base anda equipment-supporting base.

FIG. 9 is another perspective view example of an instrument-securingbase and an equipment-supporting base.

FIG. 10 is a further perspective view example of an instrument-securingbase and an equipment-supporting base.

FIGS. 11 and 12 are perspective view examples of a tower-like instrumentalignment and introduction guide assembly, also referred to as a deepbrain access device.

FIG. 13 is an exploded perspective view example of portions of a deepbrain access device.

FIG. 14 is a perspective view example of adjusting an instrumenttrajectory using portions of a deep brain access device with MRI, CT, oranother imaging modality.

FIG. 15 is a perspective view example of adjusting an instrumenttrajectory using portions of a deep brain access device with a framelesssurgical navigational system.

FIG. 16 is a perspective view example of an MRI-imagable alignment stem.

FIG. 17 is a perspective view example of an adapter for receiving aframeless surgical navigation instrument.

FIG. 18 is a perspective view example of a technique for introducing aninstrument along the previously established trajectory using a peel-awaysheath and stylet.

FIGS. 19A and 19B provide two perspective view examples of a multilumeninsert portion of a deep brain access device.

FIG. 20 is a perspective view example of a hub and stylets.

FIG. 21 is a perspective view example of a single peel-away sheath.

FIG. 22 is a perspective view example of a guide bridge mounted onto amultilumen insert of a deep brain access device.

FIG. 23 is a perspective view example of an offset guide bridge.

FIG. 24 is a perspective view example of a center guide bridge.

FIGS. 25 and 26 are perspective view examples, respectively, of a remoteintroducer mounted onto a deep brain access device.

FIG. 27 is a perspective view alternate example of aninstrument-securing base.

FIG. 28 is a perspective view example of a ball-housing socket on atranslational stage.

FIG. 29 is a perspective view example of an alternate remote introducermounted to a deep brain access device.

FIG. 30 is a cross-sectional view example of an alternate deep brainaccess device.

FIG. 31 is a perspective view example of a ball and inner sleeve withguide lumens.

FIGS. 32A and 32B provide various perspective and cross-sectional viewexamples of a peel-away sheath with depth markers, a stylet, and a deepbrain access device receiving the sheath and stylet.

FIGS. 33A, 33B, and 33C provide various perspective and cross-sectionalview examples of an alternate stabilizer.

FIGS. 34A and 34B provide various perspective view examples of anotheralternate stabilizer and accompanying tool.

FIG. 35 provides various perspective and cross-sectional view examplesof a guide alternative to the peel-away sheaths.

FIG. 36 provides a perspective and a cross-sectional view examples of asheath having rotatable components for allowing side access, which isuseful as an alternative to the peel-away sheath.

FIG. 37 is a cross-sectional view example of an alternative deep brainaccess device, mounted to a skull, and a remote introducer mounted tothe deep brain access device.

FIG. 38 is a perspective view example of an alternative deep brainaccess device providing a pivoting base, an arc-like path, and aball-and-socket movement for adjusting a trajectory of an instrumentbeing introduced into the brain.

FIG. 39 is a perspective view illustrating an alternate example of amultilumen insert including imaging-recognizable fiducial markings.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

One example of trajectory guides for surgical applications is discussedin Truwit et al., International Patent Application No. PCT/US98/10008(International Publication No. WO 98/51229), which is incorporatedherein by reference.

FIG. 1 is a cross-sectional view illustrating an example of a flexibleprimary medical instrument, such as an implanted deep brainneurostimulator electrode 100. FIG. 1 also illustrates portions of asecondary medical device, such as deep brain access device 102, andportions of a patient's brain in which electrode 100 and access device102 are used. Electrode 100 includes a distal end 100A and a proximalend 100B. Proximal end 100B emerges from under a skin flap of thepatient into which it has been inserted. Access device 102 includes,among other things, a base 104 access plate or ring securedconcentrically around and/or in a burr hole 106 in the skull. Base 104provides an access opening that is approximately the same diameter as astandard burr hole. Electrode 100 extends through burr hole 106 into atarget location 108 in the brain, and is held in place by stabilizer110. Access device 102 also includes a substantially rigid cap 112 thatcovers burr hole 106, stabilizer 110, and base plate 104, and isoverlaid by a tapered low profile flexible (e.g., silicone or otherelastomer) conformal cap 114 to soften the profile of the implantedapparatuses under the patient's scalp to more closely match the skullsurface 116.

A suitable hole in conformal cap 114 and/or the overlying skin flappermits any upturned proximal portion 100B of electrode 100 to beexposed outside the skin flap, if desired. In this example, conformalcap 114 includes an engaging lip that mates with a lip of cap 112 orbase 104. This holds conformal cap 114 in place.

In one example, portions of access device 102 allow attachment by otherapparatuses during targeting/alignment, positioning, and/or acutely orchronically securing the implanted instrument. Although designed for usewith a trajectory alignment system, stabilizer 110 can be used alone tostabilize catheters, needles, and drug and biological agent deliveryinstruments, as well as electrodes used for any purpose (e.g.,electrical mapping, stimulation, or ablation) that have been placedusing alternate targeting and placement methods and systems.

FIG. 2 is a perspective view of an example base 104. In this example,base 104 is attached to the patient's skull by any suitable fasteningdevice, such as bone screws 200A and 200B. Alternatively, base 104 issecured by threads that screw into burr hole 106. Other examples ofattachment to the skull or other portions of the patient's body includeadhesive, suction and other techniques. Base 104 includes one or moregrooves 202 for receiving the proximal end 100B of electrode 100, orother flexible instrument, which is laterally bent into groove 202 forconformally exiting base 104, so that proximal end 100B of electrode 100lies generally parallel to the skull surface 116. Proximal end 100B ofelectrode 100 extends along skull surface 116 for a clinicallyappropriate distance. Cap 112 covers portions of burr hole 106, and theassembly of base 104 and electrode 100. In this example, base 104includes recesses 204A-B, such as for receiving respective pry lipextensions 206A-B of cap 112.

FIG. 3 is an exploded view illustrating an example of an assembly ofbase 104, stabilizer 110, and cap 112. Cap 112 includes a relativelylarger top 300 and a relatively smaller, generally cylindrical base 302.Cap 112 includes male finger or female receptacle snap-fits 304 (orother attachment device(s)) that are coupled to respective mating femalereceptacle or male finger snap-fits 306 of base 104 so that, whenassembled, cap 112 is coupled to base 104, within its center opening307, and covers stabilizer 110. The cylindrical base portion 302 of cap112 includes at least one opening 308 permitting electrode 100 to exitbase 104 via groove 202.

In the example of FIG. 3, stabilizer 110 includes a disk 310 coupled toa cam 312. Cam 312 rotates, with respect to disk 310, about an axisperpendicular to the plane of disk 310, to create and substantiallyclose opening 314 in which electrode 100 is either passed freely (whenopen) or clamped (when closed) Thus, cam 312 is understood to includeany form of clamping device. FIG. 3 illustrates cam 312 in its openposition. Stabilizer 110 also includes snap-fits or other fasteningfeatures for coupling it to base 104. In the example of FIG. 3,stabilizer 110 can be snapped into base 104 in any rotationalorientation. That is, the user can rotate stabilizer 110 a full 360degrees to choose a specific rotational orientation with respect to base104, and then snap stabilizer 110 into base 104 at that orientation.Moreover, elongate opening 314 extends radially from the center of thedisk-like stabilizer 110 to its outer circumference. Along with the fullrotational coupling capability of stabilizer 110, this allows aninstrument, such as electrode 100, to be clamped within opening 314 inany location over the full area of opening 307 in base 104. Thisprovides additional precision in placing the electrode 100 or otherinstrument.

FIG. 4 is a perspective view illustrating a closer view of stabilizer110 in which cam 312 is in a closed position. FIG. 4 also illustratescoupling features 400A-B for coupling stabilizer 110 to base 104. Inthis example, one or more recesses 402A-B, or other engaging features,is provided. By using a tool that engages at least one of recesses402A-B, stabilizer 110 can be placed into base 104 and snap-coupledthereto. Cam 312 also includes one or more recess 404, or other engagingfeature. By using a tool that engages recess 404, cam 312 can be movedbetween open and substantially closed positions. In this example, cam312 also includes a catch 406 that prevents unwanted accidental movementof cam 312 into the open position when cam 312 is intended to be in theclosed position to secure electrode 100 or other medical instrument. Inthis manner, cam 312 locks into the closed position, and is opened bypressing down on a tool engaging recess 404. This allows catch 406 toslide under disk 310.

FIG. 5 is an exploded view of an alternate embodiment in whichstabilizer 110 includes strain relief features 500A-B, either of whichmay be used to secure a small amount of slack in electrode 100 or otherinstrument. Also in this example, a plurality of grooves 202 in base104, and a corresponding plurality of grooves 308 in cap 112, allowselectrode 100 to laterally exit base 104.

FIGS. 6A and 6B provide two perspective views of an example basepositioner 600 device for centering base 104 around burr hole 106 (ofknown diameter) in the skull. A distal portion 602 of positioner 600 isappropriately sized to be received into center opening 307 of base 104and further into burr hole 106. This centers base 104 concentricallyaround burr hole 106. Bone screws 200A-B are temporarily captured withinopenings in extension wings 604A-B of positioner 600, such that bonescrews 200A-B are aligned to corresponding openings in base 104. Bonescrews 200A-B are then loosely secured to the patient's skull, such thatbase 104 is properly positioned and centered around burr hole 106. Wings604A-B are scored or otherwise constructed so as to separate when bonescrews 200A-B are more securely tightened, thereby releasing bone screws200A-B so that they can fasten base 104 to the patient's skull.Positioner 600 is then removed, such as by snapping it out of base 104,leaving base 104 securely fastened in the proper position with respectto burr hole 106.

FIG. 7 is a perspective view of an example of a tool 700 for performingprocedures with respect to, among other things, base 104, cap 112,and/or stabilizer 110. In this example, tool 700 includes a handle 702,a first engaging arm 704, and a second engaging arm 706. The end of arm704 is appropriately sized to engage one of recesses 402A-B of disk 310of stabilizer 110 for placing stabilizer 110 into base 104. The end ofarm 706 is appropriately sized to engage recess 404 in cam 312 formoving cam 312 between its open and closed positions. In this example,at least one of ends 704 and 706 is appropriately sized for beinginserted into one of recesses 204A-B (see FIG. 2) of base 104, and underone of corresponding extensions 206A-B for prying cap 112 away from base104.

FIG. 8 is a perspective view of an example of a different base, such assupport base 800. In this example, support base 800 provides a ring-likeor any other (e.g., cylindrical) suitable platform 802 for supportingother surgical equipment, such as for targeting/alignment of thetrajectory of the instrument being introduced, and/or for introducingthe instrument after such proper alignment is obtained. In this example,the equipment support base 800 is separate from instrument securing base104, however, these two bases could alternatively be integrally formedor otherwise joined. In the example of FIG. 8, however, support base 800is secured directly to the patient's skull over and around securing base104, using bone screws 804A-C through legs extending downward fromplatform 802, by using any other appropriate affixation technique.

FIG. 9 is a perspective view of an alternate example of a base 800,secured directly to the patient's skull by four bone screws 804A-Dthrough respective legs extending downward from platform 802. Thisfour-legged example advantageously allows for a smaller incision (e.g.,in the direction of the instrument exit slot of base 104) into thepatient's skull than the three-legged example of FIG. 8. Because thelegs in the example of FIG. 9 are closer together than the legs in theexample of FIG. 8, the skin does not have to be laterally spread apartas far to allow placement of the example of FIG. 9. Such a reducedlateral skin-spreading in turn reduces the required length of theincision slit.

FIG. 10 is a perspective view of an alternate example of a support base800. In this example, support base 800 is secured by any suitable meansto instrument-securing base 104, which, in turn, is secured to thepatient's skull, such as discussed above. In the example of FIG. 10,legs 1000A-D space platform 802 away from base 104. Each of legs 1000A-Dincludes one or more snap-fit features 1002 for engaging correspondingmating features on base 104. Tightening screws 1004A-B are each capturedby a respective threaded portion of platform 802, and extend downward topress against base 104 when base 104 and platform 802 are snappedtogether. By adjusting screws 1004A-B, support base 800 is backed awayfrom instrument-securing base 104 so that these two bases are moretightly coupled to each other. This provides added stability to platform802.

FIGS. 11 and 12 are perspective views of an example of a tower-likeinstrument alignment and introduction guide assembly, also referred toas a deep brain access device 1100. DBA device 1100 can also be regardedas including base 104, stabilizer 110, cap 112, and support base 800. Atower base 1102 of device 1100 snaps onto and rotates upon the ring-likeor other platform 802 of FIGS. 8-10, such as by one or more snap-fittingside blocks 1104. Side blocks 1104 provide added stability to preventtower base 1102 from rocking from side-to-side on platform ring 802. Acurved saddle 1106 is coupled to and seated on a curved portion of towerbase 1102, such as by at least one arcuate sliding joint, asillustrated. The curved portions of saddle 1106 and tower base 1102 canbe tilted with respect to each other to alter a trajectory angle of aninstrument being introduced, and can be secured to fix this aspect ofthe trajectory angle of the instrument.

An affixation mechanism, such as thumbscrew 1108, passes through anopening in tower base 1102 and engages a portion of platform 802 toprevent further rotation of tower base 1102 with respect to platform 802once a desired rotational position has been obtained. In this example, acapturing device, such as L-shaped arm 1110, retains thumbscrew 1108together with tower base 1102.

Another affixation mechanism, such as thumbscrew 1112, passes through aslotted opening (tilt slot) in saddle 1106 and engages a portion oftower base 1102 to prevent further riding of the curved portion ofsaddle 1106 along the curved portion of tower base 1102 once a desiredtrajectory angle has been obtained. This example also includesattachment fasteners 1113A-B passing through corresponding slots insaddle 1106 for additionally securing saddle 1106 to tower base 1102.Attachment fasteners 1113A-B include screws passing through respectiveretainer brackets, each of which includes a curved surface conforming toa curved surface of saddle 1106.

Also in this example, an interior portion of a socket 1114 on saddle1106 provides a socket portion of a ball-and-socket joint. An affixationmechanism, such as thumbscrew 1116, passes through a threaded opening insocket 1114 to secure the position of a ball housed therein. Socket 1114also includes fine-tuning thumbscrews 1118A-C, which pass throughthreaded openings in socket 1114 for further adjusting the exactposition of a ball within socket 1114. Socket 1114 further carries amultilumen instrument guide insert assembly 1120. Multilumen insert 1120includes a tapered sleeve that is releasably coupled, by release tab1122 and associated structure(s), within a cylindrical opening throughthe spherical ball housed within socket 1114.

To release the multilumen insert 1120 from the ball, the tab 1122 ispressed inward toward the sleeve. This forces or wedges a portion of therelease tab 1122 against a top portion of the ball and aids in releasingthe multilumen insert 1120 from the ball. The top portion of multilumeninsert 1120 provides a multilumen guide having a plurality of openings,such as the center opening 1124A and side openings 1124B-E; theseopenings are also referred to as lumens. Openings 1124B-E are spacedapart from center opening 1124A by a known predetermined distance.Therefore, if electrode 100 is inserted through center opening 1124A,and misses its target location 108 in the brain, it can be inserted intoone of the side openings 1124B-E, without readjusting the trajectory, toreach a target at a known distance away from center opening 1124A in theplane of the multilumen insert 1120. In this example, multilumen insert1120 also includes T-shaped receptacles or recesses 1126A-D forreceiving further equipment, as discussed below. In one embodiment,multilumen insert 1120 includes one or more fiducial points (e.g., LEDs,reflective globes, or microcoils), such as for trajectory alignment in aframeless surgical navigation system or in an MRI environment.

FIG. 13 is an exploded perspective view of an example of portions ofdeep brain access device 1100, including instrument-securing access base104, support base 800, tower base 1102, saddle 1106, socket 1114A, ball1300, multilumen insert 1120, and other associated components. Asillustrated in FIG. 13, tower base 1102 includes a bottom or grooveportion 1302 that engages platform 802, such as using hooked side blocks1104, and allows tower base 1102 to rotate about the ring-like or otherplatform 802.

FIG. 13 also illustrates a cylindrical opening 1306 through ball 1300,which is seated in socket 1114A. Multilumen insert 1120 includes atapered sleeve 1308 or barrel portion that fits snugly within opening1306. Release 1122 includes a ring portion that fits over the exteriorof sleeve 1308. To release multilumen insert 1120 from ball 1300, thetab portion of release 1122 is pressed inward toward sleeve 1308. Thisforces or wedges a portion of release 1122 against the top portion ofball 1300 and aids in releasing sleeve 1308 of multilumen insert 1120from ball 1300. The tapered barrel provided by sleeve 1308 of multilumeninsert 1120 includes, in one example, a closed end with openingscorresponding to lumens 1124A-E of multilumen insert 1120.

FIG. 14 is a perspective view illustrating an example of adjusting aninstrument trajectory using portions of deep brain access device 1100with MRI, CT, PET, or another imaging modality. In FIG. 14, multilumeninsert 1120 has been removed, and an imagable reference device, such asalignment stem 1400, has been inserted into the cylindrical passagewayof ball 1300 in its place. In this example, alignment stem 1400 includesat least two fiducial points that are recognizable by the imagingmodality. The various above-described positioning mechanisms of deepbrain access device 1100 are adjusted to make the fiducial pointscollinear with the target location 108 in the brain. In one example,this may include adjusting the rotation of tower 1102 on platform 802,adjusting the tilt of saddle 1106 with respect to tower 1102, adjustingthe spherical position of ball 1300 within socket 1114, and then finetuning the exact position of ball 1300 using one or more of screws1118A-C. The imaging modality includes a computer or other processorthat provides a display indicating the relative alignment between thetrajectory of alignment stem 1400 and target location 108. This displayfurther indicates when the trajectory becomes collinear with targetlocation 108 during the positioning process. The positioning mechanismsprovide locking devices that are then locked in, and the alignment stem1400 is replaced by multilumen insert 1120 for continuing the procedureof introducing electrode 100 or other instrument along this trajectoryto target location 108 in the brain.

FIG. 15 is a perspective view illustrating an example of adjusting aninstrument trajectory using portions of deep brain access device 1100 inconjunction with a frameless surgical navigational system. Examples ofsuch systems use LEDs, light reflecting globes, or otherspatially-separated fiducial markers to establish a desired instrumenttrajectory orientation. In the frameless example of FIG. 15, multilumeninsert 1120 remains in place within the cylindrical passageway of ball1300. Adapter 1500 is inserted into center lumen 1124A of multilumeninsert 1120. In this example, adapter 1500 includes a center-bored seat1502 that snugly receives a portion of frameless navigation referencedevice instrument. The frameless navigation reference instrumentprovides spatially-separated fiducial points that are recognized by theframeless imaging modality. These fiducial points are viewed, using theappropriate imaging modality, while the various positioning mechanismsof the deep brain access device are adjusted, to orient the instrument'strajectory toward the desired target location 108 in the brain, thenlocked in. The frameless navigation instrument is then removed fromcenter-bored seat 1502 of adapter 1500. Adapter 1500 is then removedfrom center lumen 1124A of multilumen insert 1120 for continuing theprocedure of introducing electrode 100 or other instrument along thistrajectory to brain target location 108.

FIG. 16 is a perspective view illustrating an example of alignment stem1400 when separated from deep brain access device 1100. In this example,alignment stem 1400 is filled with an imagable fluid provided through aone-way valve 1600 at a proximal end of alignment stem 1400. A distalend of alignment stem 1400 includes a protuberance or other extension1602. In this example, extension 1602 is a thin cylindrical containerhaving a distal tip 1604. Distal tip 1604 is located at the pivot pointof ball 1300 when ball 1300 is seated in socket 1114 of saddle 1106. Inthis example, imagable fiducial points are provided at proximal valve1600 and distal tip 1604. The trajectory is established by adjusting thevarious positioning mechanisms of deep brain access device 1100 so thatthese imagable fiducial points are collinear with target location 108 inthe brain. In one example, the exact position of target location 108 isobtained using real-time imaging of the brain while the positioningmechanisms of deep brain access device 1100 are being adjusted. Inanother example, preoperative brain images are used to determine theposition of target location 108 while adjusting the various positioningmechanisms of deep brain access device 1100. FIG. 16 also illustrates arelease mechanism 1606, which includes knob 1608 and ramp 1610. Byimparting a force on knob 1608 toward ball 1300, ramp 1610 engages thetop of ball 1300 to assist in releasing alignment stem 1400 from thecylindrical passageway of ball 1300. Then, multilumen insert 1120 isreinserted into the cylindrical passageway of ball 1300, for introducingelectrode 100 or other medical instrument(s) through lumen(s) 1124 ofmultilumen insert 1120.

FIG. 17 is a perspective view illustrating an example of framelessadapter 1500 when separated from deep brain access device 1100. In thisexample, adapter 1500 includes stainless steel pin, having a distal tip1700, that is appropriately sized for being inserted into center lumen1124A of multilumen insert 1120. When fully inserted, distal tip 1700 islocated the pivot point of ball 1300 when ball 1300 is seated in socket1114 of saddle 1106. In this example, a frameless navigation instrumentwith frameless imagable fiducial points is inserted into center-boredseat 1502 at the proximal end of adapter 1500, or onto the outer portionof adapter 1500, or otherwise coupled to adapter 1500 by any otherappropriate coupling technique.

FIG. 18 is a perspective view illustrating an example of a technique forintroducing an instrument along the previously established trajectory totarget location 108 in the brain. In FIG. 18, multilumen insert 1120 isused to guide a distal end of a secondary medical instrument, such as anelongate lumenal catheter or peel-away sheath, for example, one ofsheaths 1800A-C, toward target location 108. Before sheath 1800 isinserted into one of lumens 1124A-E of multilumen insert 1120, however,a stylet is inserted through a hollow center bore or lumen of sheath1800. This prevents coring of brain tissue by the hollow center bore ofsheath 1800 and, in one embodiment, provides additional rigidity forperforming the insertion and obtaining an accurate path along theestablished trajectory toward target location 108.

The example of FIG. 18 illustrates a triple sheath assembly 1802, withlinearly-arranged sheaths 1800A-C, appropriately spaced apart for beinginserted into three linearly-arranged lumens 1124 of multilumen insert1120. This example similarly illustrates a triple stylet assembly 1804in which three linearly-arranged stylets are spaced apart for insertionin the linearly-arranged sheaths 1800A-C. This triple sheath/styletillustration is merely an example. The exact number of sheaths 1800 andcorresponding stylets being introduced ranges from a singlesheath/stylet to the number of available lumens 1124 in multilumeninsert 1120. After sheath assembly 1802 and stylet assembly 1804 hasbeen guided approximately to target location 108, stylet assembly 1804is removed and a guide bridge is secured to multilumen insert 1120 forguiding electrode 100 into the center bore of one of sheaths 1800A-C forpositioning electrode 100 at target location 108. The sheaths 1800A-Care then removed by pulling apart handles 1806A-B. In the illustratedexample, each sheath 1800 breaks into two pieces as it is beingextracted.

FIGS. 19A and 19B provide two perspective views of an example ofmultilumen insert 1120, which includes the tapered barrel-like sleeve1308 that is inserted into center hole 1306 of ball 1300. Lumens 1124A-Eextend from the top of multilumen insert 1120 through the barrel sleeve1308. As discussed above, side lumens 1124B-E are appropriatelyradially-spaced (e.g., 3 millimeters, center-to-center) from centerlumen 1124A to provide capability for repositioning of electrode 100 bya known amount by simply removing electrode 100 from center lumen 1124Aand reinserting it into a desired one of side lumens 1124B-E. FIGS. 19Aand 19B also illustrate receptacles 1126A-D, opposing pairs of which areused for receiving a guide bridge or other equipment desired to bemounted to the top of multilumen insert 1120.

FIG. 20 is a perspective view illustrating an alternate example of astylet assembly 2000, including a hub 2002 for uniting 1-5 stylets2004A-C for insertion into corresponding peel-away or other sheathsinserted through corresponding lumens 1124 of multilumen insert 1120. Inone embodiment, hub 2002 includes a Touhy-Borst adapter, or othersuitable adapter for gripping stylets 2004A-C.

FIG. 21 is a perspective view illustrating an example of a singlepeel-away sheath 2100 including a distal tip 2102, a proximal end 2104,and a center bore or lumen extending therebetween. Handles 2106A-B areincluded at proximal end 2104. Sheath 2100 is peeled away and extractedby pulling apart handles 2106A-B.

FIG. 22 is a perspective view illustrating an example of a guide lumenselector, such as guide bridge 2200 having tabs or legs that aresnap-mounted onto an opposing pair of receptacles 1126A-D of multilumeninsert 1120. In this example, guide bridge 2200 includes a cylindricalguide tube 2202 extending upward from a base portion of guide bridge2200. Guide tube 2202 includes a center bore hole 2204 for passingelectrode 100 or other instrument therethrough. A proximal portion ofguide tube 2202 includes a lip 2206 extending outward circumferentiallyaround the perimeter of guide tube 2202. In one example, the center borehole 2204 is tapered inward in a direction away from lip 2206. That is,an inner diameter of bore hole 2204 necks down so the instrument passedtherethrough is automatically centered as it approaches the base portionof guide bridge 2200. In this example, guide bridge 2200 also assists inholding the sheath(s) in place as the electrode is being passed througha sheath to target location 108. The handle portions of the sheath donot pass through guide tube 2202, but instead, exit under the sides ofguide bridge 2200. In one example, guide bridge 2200 includes awedge-like ridge on its underside to assist in splitting the peel-awaysheath.

FIGS. 23 and 24 are perspective views illustrating an offset guidebridge 2300 and a center guide bridge 2400, respectively. Lumens 1124A-Eprovide a primary guide device for electrode 100 or other instrument,and the selected one of offset guide bridge 2300 and center guide bridge2400 provides a secondary guide device for electrode 100 or otherinstrument. Offset guide bridge 2300 is selected when the instrumentbeing introduced is intended to pass through one of side lumens 1124B-Ein multilumen insert 1120. In this example, guide tube 2202 is offsetfrom the center of the base of offset guide bridge 2300, such that itscenter bore 2204 is aligned with one of side lumens 1124B-E ofmultilumen insert 1120. Alignment with the particular desired side lumenis obtained by appropriately rotating the orientation of offset guidebridge 2300 and snapping tabs 2302A-B into corresponding opposing pairsof receptacles 1126. By contrast, in center guide bridge 2400, guidetube 2202 is centered on the base portion of center guide bridge 2400,such that its center bore 2204 aligns with center lumen 1124A ofmultilumen insert 1120 when center guide bridge 2400 is snapped intoopposing pairs of receptacles 1126 of multilumen insert 1120. In each ofthe examples of FIGS. 23 and 24, an outside portion of lip 2206 isthreaded for engaging other equipment. Alternatively, other equipmentmay be mounted onto guide tube 2202 by using a compression fit to athreaded or unthreaded lip 2206.

FIGS. 25 and 26 are perspective views of deep brain access device 1100,on which a center guide bridge 2400 is mounted to multilumen insert1120. In these examples, an introducer 2500 mechanism is mounted ontoguide tube 2202 using a compression fitting to lip 2206. Introducer 2500includes a slide 2502 mechanism on which a sliding clamp 2504 ridestoward and away from deep brain access device 1100 and, therefore,toward and away from burr hole 106 in the skull or other entry portal.Clamp 2504 holds the electrode 100 or other instrument being introduced.In one example, introducer 2500 is operated remotely by controls 2506A-Bto slide clamp 2504 along slide 2502, and therefore, to introduce theinstrument being held by clamp 2504 into and/or out of the brain alongthe predetermined trajectory in a controlled manner. One example of anappropriate remote introducer 2500 is the Fathom®. Remote Introduceravailable from Image-Guided Neurologics, Inc. of Melbourne, Fla. U.S.A.Another example of an appropriate remote introducer 2500 is described inSkakoon et al. U.S. patent application Ser. No. 09/827,266, filed onApr. 5, 2001, now U.S. Pat. No. 7,660,621, issued on Feb. 9, 2010,entitled “Medical Device Introducer,” and assigned to the assignee ofthe present patent application, the disclosure of which is incorporatedherein by reference in its entirety.

FIG. 27 is a perspective view of an alternate example of aninstrument-securing base 2700. In this example, base 2700 is centeredaround burr hole 106 and secured to the skull using bone screws 2702A-Dextending through openings in leg portions. Base 2700 includes twoopposing mating slides 2704A-B that move toward and away from eachother, and that mate and engage each other to clamp electrode 100 orother instrument therebetween. One or more slots 202 are provided forproviding a lateral exit for electrode 100, as discussed above. Otherequipment is either attached directly to the skull around base 2700, orattached indirectly to the skull, though base 2700, such as by snappingor clamping such equipment to receiving sides 2706A-B.

FIG. 28 is a perspective view of a ball-housing socket 2800, used as analternative to socket 1114. In this example, socket 2800 rides on asliding translational stage 2802 on a mount 2804 coupled to saddle 1106or other portion of deep brain access device 1100. This example includesa squeeze release 2806 for disengaging mount 2804 from saddle 1106 orother affixation point of deep brain access device 1100. Alternatively,mount 2804 is affixed to securing base 2700 by a hooked engagementmechanism 2808 that engages an underside of securing base 2700, or byusing any other appropriate coupling technique. Thumbscrew 2810 engagesa threaded opening in mount 2804 and also engages and controlstranslational movement of sliding stage 2802. Thumbscrew 2812 engages athreaded opening in mount 2804 and secures the position of stage 2802 toprevent unwanted translational movement after its desired position isobtained. Either thumbscrew may be captured to prevent accidentalseparation from mount 2804.

FIG. 29 is a perspective view illustrating a remote introducer 2900,provided as an alternative to introducer 2500. In this example,introducer 2900 is coupled to a portion of deep brain access device2901, such as by using a Touhy-Borst adapter 2902 threaded onto a lip ofa guide tube, similar to lip 2206 of guide tube 2202. In this example,electrode 100 is inserted through a peel-away sheath 2100 (afterremoving a stylet). Sheath 2100 is secured to a squeeze-release clamp2904 that slides toward and away from the skull along slide 2906. Inthis example, advancement and retraction of clamp 2904 is remotelycontrolled using controls 2506A-B.

FIG. 30 is a cross-sectional view illustrating a deep brain accessdevice 3000, provided as an alternative to deep brain access device1100. In this example, base 104 is secured to the skull using bonescrews. A pedestal or tower 3002 is secured to base 104 as illustratedor, alternatively, is secured directly to the skull. Tower 3002 includesa socket 3004 housing a ball 3006. Ball 3006 includes a center openingthat receives a rotating inner barrel sleeve 3008. In this example,sleeve 3008 includes one or more lumens 3010A-C extending therethroughfor passing and guiding instruments, sheaths, stylets, etc. Anaffixation device, such as thumbscrew 3012, fixes the position of ball3006 when the desired trajectory alignment has been obtained, such as byusing the MRI, CT, PET, or frameless navigational guidance techniquesdiscussed above. Proximal portions of lumens 3010A-C include recessesfor snapping into place lips on devices inserted therein, such asalignment stem (or frameless adapter) 3014 and/or Luer stem 3016. Aremote introducer may be attached to Luer stem 3016, as discussed above.Luer stem 3016 may include a wedge 3018, for assisting in splitting apeel-away sheath inserted through corresponding lumen 3010 before Luerstem 3016 is inserted therein. Luer stem 3016 may also includeorientation tabs 3020 to appropriately align the wedge to provide thedesired assistance in splitting the peel-away sheath.

FIG. 31 is a perspective view illustrating an example of ball 3006 andsleeve 3008, including an illustration of the ball-and-socket movementof ball 3006 and rotational movement of sleeve 3008 within ball 3006. Inthis example, lumens 3010 include associated transverse grooves 3100extending laterally in opposite directions from the lumens 3010 toopposing edges of sleeve 3008. Grooves 3100 receive and/or holdpeel-away portions of one or more peel-away sheaths inserted intorespective lumens 3010.

FIGS. 32A and 32B provide various perspective and side views of portionsof deep brain access device 3000 and associated components. In thisexample, a three prong titanium stylet 3200 assembly is inserted intocorresponding lumens of a triple peel-away plastic sheath 3202 assembly.One or more prongs of sheath 3202 includes depth markers 3204. Thecombined sheath 3202 and stylet 3200 is inserted into correspondinglumens 3010 of guide sleeve 3008 to the desired depth, as indicated bydepth markers 3204 on sheath 3202. The proximal portion of sheath 3202is then separated as illustrated in FIG. 32B and flattened outlaterally. Wedge 3206 on a proximal handle portion of stylet 3200 mayassist in splitting sheath 3202. This establishes the prongs of sheath3202 at the desired depth. Stylet 3200 is then removed, and electrode100 or another instrument is introduced into position through the sheath3202.

FIGS. 33A, 33B, and 33C provide exploded perspective and cross-sectionalviews of a stabilizer 3300, which can serve as an alternative tostabilizer 110. In this example, stabilizer 3300 includes asubstantially rigid ring-like base 3302, a substantially rigid upperplate, 3304, and a soft middle plate 3306 interposed between upper plate3304 and lower ring 3302. Upper plate 3304 and middle plate 3306 includecorresponding openings 3308. A neurostimulating electrode 100 or otherinstrument is passed through one of these openings 3308. A soft maleprotuberance around the opening in middle plate 3306 is received withina female receptacle around the opening in upper plate 3304. When upperplate 3304 is clamped down against base 3302, the soft protuberance issqueezed against the electrode 100, holding it securely in place.

FIGS. 34A and 34B are perspective views of a stabilizer 3400, whichprovides an alternative to stabilizer 110. In this example, stabilizer3400 is rubber or any other flexible material that tends to return toits original shape. The stabilizer 3400 can include a variable openinghaving first and second longitudinal walls facing each other in spacedrelation. The first and second walls can extend along a longitudinalaxis from an open end at a periphery of the stabilizer 3400 radiallyinward towards a closed end. In this manner, the variable opening caninclude a substantially uniform width from the periphery to the closedend when in the original shape. A pair of spaced apart apertures can beformed in a top surface of the stabilizer such that the longitudinalaxis of the variable opening extends through a center of each aperture.A portion of each aperture can form an arcuate depression in the firstlongitudinal wall and another portion of each aperture can form anarcuate depression in the second longitudinal wall. One of the aperturescan form the closed end of the opening. A spreader 3402 is used to openthe variable opening or slot 3406 in stabilizer 3400, which is theninserted into an instrument-securing base-plate fastened to the skull.When electrode 100 or other instrument is properly positioned, thespreader is removed, allowing stabilizer 3400 to return to its originalshape with the slot 3406 closed around the electrode 100 to hold itsecurely in place.

The spreader 3402 can include a pair of spaced apart projectionsextending transversely therefrom that can be inserted into theapertures. The spreader 3402 can be rotated relative to the stabilizerto expand the variable opening to a deformed shape. In an exemplaryconfiguration, the spreader 3402 can be inserted into the apertures suchthat a longitudinal axis of the spreader is substantially perpendicularto the longitudinal axis of the opening. The spreader 3402 can then berotated to expend the variable opening to a deformed shape where thelongitudinal axis of the spreader is substantially parallel to the axisof the opening.

FIG. 35 provides a perspective view and several cross-sectional viewsillustrating a sheath-substitute guide 3500, which provides analternative to the peel-away sheaths discussed above. In this example,guide 3500 includes one or more elongate guides 3500A-C that do not havea central bore lumen for guiding an instrument through. Instead, eachguide 3500A-C includes a cross-section that is formed for guiding aninstrument along its side. In this example, the cross-section iscrescent-shaped so as to provide a degree of mating to the outerdiameter of electrode 100, stylet 3502, or other instrument that isintroduced into the patient along the side of the guide 3500. In oneexample, guide 3500 is introduced in tandem with removable stylet 3502,which provides additional rigidity to the introduction process. Inanother example, guide 3500 is introduced without removable stylet 3502.Because guide 3500 does not use a central bore lumen, coring of braintissue during its introduction may be of less concern. Guide 3500 allowsaccess to the adjacent electrode 100 along its entire length, allowingelectrode 100 to be gripped and/or secured very close to the skull (suchas using instrument-securing base 104) before guide 3500 is removed.This prevents excessive movement of electrode 100 during extraction ofguide 3500, which provides more accurate placement of electrode 100 orother instrument.

FIG. 36 provides a perspective view and a cross-sectional viewillustrating a sheath 3600 assembly, which provides another alternativeto the peel-away sheaths discussed above. In this example, sheath 3600assembly includes one or more elongate sheaths 3600A-C. Each elongatesheath 3600 includes an open slot along its length, or a portionthereof. In the illustrated example, each elongate sheath 3600 includestwo C-shaped portions 3602A-B that rotate with respect to each other bymanipulating a handle portion of the sheath 3600. When the C-shapedportions 3602A-B are rotated into a closed position, they togethereffectively provide a central lumen 3604 through which electrode 100 orother instrument may be passed. When the C-shaped portions 3602A-B arerotated into an open position, they together effectively provide an openslot along their length, allowing access to electrode 100 or otherinstrument that has been inserted therethrough. This allows electrode100 to be gripped and/or secured very close to the skull (such as usinginstrument-securing base 104) before sheath 3600 is removed. Thisprevents excessive movement of electrode 100 during extraction of sheath3600, which provides more accurate placement of electrode 100 or otherinstrument. In this example, stylet(s) may be inserted into the lumen3604 before sheath 1600 is introduced, to avoid coring of brain tissue.

FIG. 37 is a cross-sectional view illustrating an example of deep brainaccess device 3000 mounted onto the patient's skull with remoteintroducer 2500 mounted onto Luer stem 3016, which is snapped intocentral lumen 3010B. Neurostimulating electrode 100 is held byintroducer 2500, and passed through central lumen 3010B to targetlocation 108 of the brain.

FIG. 38 is a cross-sectional view illustrating an alternate example of adeep brain access device 3800. This example illustrates a base 3802,which is centered around burr hole 106 and secured to the skull. A tower3804 is secured to base 3802 or, alternatively, directly to the skull.Tower 3804 includes mounting legs 3806 and 3808, which are affixed tobase 3802 or to the skull. The mounting legs 3806 and 3808 are coupledto a pedestal 3810 by pivot pins 3812 and 3814. Pins 3812 and 3814 arealigned to provide a longitudinal axis about which pedestal 3810 pivotsuntil locked in place by thumbscrew 3816, which engages one of the pins3812 and 3814. Thus, pedestal 3810 would be capable of pivoting into andout of the drawing of FIG. 38.

In the example of FIG. 38, pedestal 3810 includes an arc 3818 extendingbetween leg extensions 3820A-B that are coupled to pivot pins 3812 and3814. Arc 3818 is curved, so that a center portion 3822, away from legextensions 3820A-B, would be more distant from the viewer of FIG. 38than the portions of arc 3818 that are closer to leg extensions 3820A-B.Arc 3818 includes a slot 3824 extending substantially along its lengthbetween leg extensions 3820A-B. A socket 3826 engages and rides alongslot 3824, until locked into position by securing thumbscrew 3828against arc 3818. Socket 3826 houses a ball 3006 that can be adjustedspherically until locked into place by one or more thumbscrews. Ball3006 includes a center sleeve 3008 having one or more lumens, asdiscussed above with respect to FIG. 30. In the example of FIG. 38, aLuer stem 3016 is snapped into a center lumen of sleeve 3008, and aremote introducer 2500 is mounted onto the Luer stem for guidingelectrode 100 to target location 108.

FIG. 39 is a perspective view illustrating an alternate example of amultilumen insert 1120. In this example, multilumen insert 1120 includesone or more fiducial markers 3900A-C (e.g., LEDs, reflective globes, orMRI-imagable microcoils), such as for trajectory alignment in aframeless surgical navigation system or in an MRI environment. Thisillustration shows three such imagable fiducial markers 3900A-C defininga plane. Fiducials 3900A-C are supported on respective arms extendingfrom an attachment extension 3902, which is coupled by an fastener, suchas screw 3904, to an arm 3906 that extends upward and outward from theplanar face plate 3908 of multilumen insert 1120. This coupling isperformed (e.g., using integral alignment guides or, alternatively,performing a calibration adjustment) so that a predetermined knownspatial relationship exists between the plane formed by imagablefiducials 3900A-C and the plane of face plate 3908, which is orthogonalto the instrument trajectory axis through each of lumens 1124A-E.Consequently, imaging fiducials 3900A-C are viewed in conjunction withadjusting the various positioning mechanisms of the deep brain accessdevice to obtain and fix the desired instrument trajectory with respectto the entry portal. Although, in this example, imaging fiducials3900A-C are illustrated as being attached and in a known spatialrelationship to plate 3908, imaging fiducials 3900A-C may alternativelybe attached to any other component of the deep brain access device so asto establish a known spatial relationship between the fiducials 3900A-Cand an axial trajectory provided by one or more of lumens 1124A-E. Asanother alternative, any component of the deep brain access deviceincludes an adapter for receiving one of several commercially availablesurgical navigation instruments. Such surgical navigation instrumentssimilarly provide imaging-recognizable fiducials. Such an adapter shouldbe oriented such that the spatial relationship between the surgicalnavigation instrument and the instrument trajectory is known, therebyallowing imaging of the fiducials to assist in adjusting the trajectoryto target location 108.

The discussed devices and methods may be used in with frameless surgicalnavigation or with MRI or other imaging. Such techniques permitreal-time determination and confirmation of anatomical placement of theinstrument for improving targeting and placement accuracy. Otheradvantages include, among other things, an alignment apparatus that usesa localized coordinate system in which positioning and aligning is basedon a coordinate system relative to the patient's skull and the skullentry point rather than a stereotactic frame; real-time imaging thateliminates the need for retrospective imaging and also allows directconfirmation of the anatomical placement; an anatomically determinedinitial targeting angle (the angle between the body or skull surface andthe theoretical target) that is selected based on the patient's actualanatomy; a unique center-of-arc principle using rotation about thenominal trajectory axis, thus simplifying optimization of the firstangular adjustment; a locking ball-and-socket arrangement for easy andaccurate direct targeting under real-time imaging or frameless surgicalnavigation; peel-away or alternative sheaths that allow the device to beeasily secured into position; access to the base plate assembly so thatthe electrode can be captured at the surface of the skull immediatelyafter successful placement and before disassembly of the targetingapparatus; and visible (under the imaging method chosen, e.g., under CTor MRI) alignment stems.

Similarly, the stabilization system provides for in situ stabilizationimmediately upon proper placement, through use of a disk and camarrangement, thus eliminating inadvertent movement during disassembly ofthe alignment apparatus, and reducing the likelihood of the electrodemoving after implantation; the snap-fit solid cap protects the electrodeand its capture mechanism from damage; the stabilization system issubstantially sealed to minimize ingress and egress; the base plate issecurely attached to the body; a special tool facilitates placement ofthe base plate correctly into the burr hole, thus assuring adequateclearance for proper assembly of all parts, as well as pre-positioningapparatus for easy attachment; and the electrode is captured by clampingit in a gap between two parts, therefore electrode damage cannot occurbecause the gap size is limited by a physical stop.

Although the examples primarily discuss targeting, placement, andstabilization of a deep brain electrode, this is just an example of oneof the possible procedures that can be done using the body portal typetrajectory guide. Numerous other procedures will be accomplished usingthis device. In addition, the device will give rise to other futuresurgical procedures.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method for securing an instrument relative to aburr hole, comprising: positioning a base relative to the burr hole witha base positioning device, the base defining a central opening and anouter perimeter having a pair of attachment portions extendingtherefrom; securing the base to a surface surrounding the burr hole witha pair of bone screws detachably retained to the base positioningdevice, each screw received in an aperture in one of the attachmentportions; engaging the bone screws with a screwdriver to secure the baseto the surface surrounding the burr hole and to release the bone screwsfrom the base positioning device upon tightening the bone screws to thebase; positioning a stabilizer relative to the base and the instrument,the stabilizer having a body defining a slot extending through the bodyand inward from an outer circumference of the body; moving a clampingdevice moveable within the slot from an open position where the slot isat least substantially unobstructed by the clamping device to allow theinstrument to pass into the slot to a closed position to secure theinstrument relative to the base; positioning the instrument into aradially extending slot formed in an upper surface of the base; andattaching a cover to the base by attaching fingers extending from aperimeter of the cover to receptacles formed in the base such that thecover secures the instrument in the radially extending slot and in anopening formed in a cylindrically extending portion of the cover.
 2. Themethod of claim 1, further comprising using a tool to move the clampingdevice relative to the slot to secure the instrument relative to thebase.
 3. The method of claim 2, wherein using the tool further includesengaging the tool into a recess formed in the stabilizer to move theclamping device.
 4. The method of claim 1, wherein positioning thestabilizer relative to the base and the instrument includes using a toolto move the stabilizer relative to the base.
 5. The method of claim 4,wherein using the tool to position the stabilizer further includesengaging the tool within a recess of the stabilizer to position thestabilizer relative to the base.
 6. The method of claim 1, whereinpositioning the stabilizer relative to the base includes positioning thestabilizer in a central opening defined by the base.
 7. The method ofclaim 6, further comprising rotating the stabilizer relative to the baseto a desired circumferential orientation of the slot relative to thebase before positioning the stabilizer within the central opening. 8.The method of claim 1, wherein attaching the cover to the base includesreceiving the cylindrical portion of the cover in a central openingdefined by the base, and removably attaching the fingers extending fromthe perimeter of the cover to the receptacles formed in the base in asnap-fit manner.
 9. The method of claim 1, further comprising attachingthe cover to the base to substantially cover the burr hole, a portion ofthe instrument, and a central opening defined by the base.
 10. Themethod of claim 1, wherein the instrument is a deep brain stimulatorelectrode and the method further comprises positioning the electrode inthe radially extending slot formed in the upper surface of the basebetween an outer perimeter and a central opening of the base.
 11. Themethod of claim 10, further comprising: laterally bending the electrodeinto the radially extending slot; and attaching the cover to the base tosecure the laterally bent electrode in the radially extending slot. 12.The method of claim 1, wherein positioning the base relative to the burrhole includes removably coupling the base positioning device to the baseto facilitate positioning the base about the burr hole; and removing thebase positioning device from the base prior to positioning thestabilizer relative to the base.
 13. The method of claim 1, furthercomprising providing a guide assembly for introducing and guiding theinstrument through the burr hole and the base and relative to a brain ofa patient.
 14. The method of claim 1, wherein moving the clamping devicewithin the slot includes rotatably moving the clamping device within theslot about an axis perpendicular to a plane of the body.
 15. The methodof claim 1, wherein attaching the cover to the base includes positioninga first and a second pair of spaced apart fingers extending from thecover into a corresponding first and second pair of receptacles in thebase to snap fit the cover to the base.
 16. The method of claim 1,wherein the clamping device locks into a substantially closed positionupon moving the clamping device to the closed position and is opened bypressing a tool into an aperture positioned in the stabilizer.
 17. Themethod of claim 1, wherein the instrument is a deep brain stimulatorelectrode and the method further includes positioning the deep brainstimulator electrode in a brain of a patient and securing the electroderelative to the base with the clamping device and the cover.
 18. Amethod for securing an instrument relative to a burr hole, comprising:positioning a base relative to the burr hole with a base positioningdevice, the base defining a central opening and an outer perimeterhaving a pair of attachment portions extending therefrom; detachablypositioning a pair of bone screws with the base positioning device, thebone screws configured to be received in the attachment portionsextending from the outer perimeter of the base; securing the base to asurface surrounding the burr hole by engaging the bone screws with ascrewdriver and driving the screws into the attachment portions torelease the bone screws from the base positioning device upon tighteningthe bone screws to the base; positioning a stabilizer relative to thebase and the instrument where the stabilizer includes a body defining aslot extending through the body and inward from an outer circumferenceof the body; moving a clamping device moveable within the slot from anopened position to a closed position to secure the instrument within theslot and relative to the base; and attaching a cover to the base to atleast substantially cover the central opening and the burr hole.
 19. Themethod of claim 18, further comprising using a tool to move the clampingdevice to secure the instrument relative to the slot and the base. 20.The method of claim 19, wherein using the tool further includes engagingan end of the tool into an aperture formed in the stabilizer to move theclamping device.
 21. The method of claim 18, further comprising using atool to rotationally position the stabilizer relative to the base. 22.The method of claim 21, wherein using the tool includes engaging thetool to an aperture formed in the stabilizer.
 23. The method of claim18, further comprising laterally bending the instrument into a radiallyextending slot formed in an upper surface of the base between the outerperimeter and the central opening; wherein attaching the cover to thebase includes attaching fingers extending from a perimeter of the coverto receptacles formed in the base in a snap-fit manner such that thecover secures the laterally bent instrument in the radially extendingslot and an opening formed in a cylindrically extending portion of thecover.
 24. The method of claim 18, wherein positioning the stabilizerrelative to the base and the instrument includes positioning thestabilizer relative to the instrument and in the central opening of thebase such that the instrument is slidably received within the slot andthe clamping device from the outer perimeter of the stabilizer.
 25. Themethod of claim 18, wherein positioning the base relative to the burrhole includes removably coupling the base positioning device to the baseto facilitate positioning the base about the burr hole; and removing thebase positioning device from the base prior to positioning thestabilizer within the central opening of the base.
 26. The method ofclaim 18, wherein moving the clamping device within the slot includesrotatably moving the clamping device within the slot about an axisperpendicular to a plane of the body.
 27. The method of claim 18,wherein the clamping device locks into a substantially closed positionupon moving the clamping device to the closed position and is opened bypressing a tool into an aperture positioned in the stabilizer.
 28. Themethod of claim 18, wherein the base positioning device includes a pairof opposed wings retaining the pair of bone screws such that uponengaging the bone screws with the screwdriver and driving the screwsinto the attachment portions, the wings release the bone screws from thebase positioning device so that the bone screws fasten the base relativeto the burr hole.
 29. A method for securing an instrument relative to aburr hole comprising: positioning a base relative to the burr hole witha base positioning device, the base defining a central opening and anouter perimeter having a pair of attachment portions extendingtherefrom; securing the base to a surface surrounding the burr hole witha pair of bone screws detachably retained to the base positioningdevice, each screw received in an aperture in one of the attachmentportions; engaging the bone screws with a screwdriver to secure the baseto the surface surrounding the burr hole and to release the bone screwsfrom the base positioning device upon tightening the bone screws to thebase; positioning a stabilizer relative to the base and the instrument,the stabilizer having a body defining a slot extending through the bodyand inward from an outer circumference of the body; moving a clampingdevice moveable within the slot with a tool from an open position wherethe slot is at least substantially unobstructed by the clamping deviceto allow the instrument to pass into the slot to a closed position wherethe clamping device substantially obstructs the slot so as to secure theinstrument relative to the base; and attaching a cover to the base to atleast substantially cover the central opening and the burr hole.
 30. Themethod of claim 29, further comprising removably coupling the basepositioning device to the base.
 31. The method of claim 29, whereinattaching the cover to the base includes attaching the cover to the baseby positioning opposed pairs of projections extending from the coverinto corresponding opposed pairs of receptacles formed in the base andaligning an opening in a sidewall of the cover with the instrument. 32.The method of claim 29, wherein moving the clamping device within theslot includes rotatably moving the clamping device within the slot aboutan axis perpendicular to a plane of the body.
 33. The method of claim29, wherein the clamping device locks into a substantially closedposition upon moving the clamping device to the closed position and isopened by pressing a tool into an aperture positioned in the stabilizer.34. The method of claim 29, wherein the instrument is a deep brainsimulator electrode and the method further includes positioning the deepbrain stimulator electrode in a brain of a patient and securing theelectrode relative to the base with the clamping device and the cover.